Situation 1: Windows XP machine can still be logged in.
If you have forgotten or lost Windows XP password, but you can still log in to the system with another user, there are two ways you can regain access to the account so that you won’t lose privilege to any program, document stored in that account.

Way 1: Reset lost password Windows XP from Control Panel.
Step1: Log in with the accessible user.
Step2: Click Start, Control Panel and User Accounts in order.
Step3: Pick the specified Windows account whose password you want to reset.
Step4: Click on Remove the password.
Step5: Now restart your PC and log in with the target user. (Note: No password is needed.)

Way 2: Change lost Windows password XP from Computer Management.
Step 1: Log on your XP profession computer with the accessible user.
Step 2: Right-click Computer and select Manage.
Step 3: Click Local User and Groups, and then click Users. And all the accounts will be listed for you.
Step 4: Right-click target account and select Set password.
Step 5: Leave the password text field blank and click OK.

Situation 2: Windows XP machine has been locked already.
To reset a forgotten or lost password on Windows XP when there is still access to the computer is pretty simple. However, when there is no access to XP machine, the above ways won’t work at all since the situation would become complicated. Though complicated the situation is, we can still find effective ways to cope with it. Below is the exact way to reset a lost XP password.

Way 3: Use Windows Password Recovery Tool.
Windows Password Recovery Tool 3.0 is powerful lost Windows password reset software. No matter the password you’ve lost is a local or a domain password on any Windows operating system, Windows Password Recovery Tool can help you solve all the possible lost Windows password problems.Here’s how Windows Password Recovery Tool works:
Step1: Download and install, run the Windows Password Recovery Tool 3.0 on an accessible computer.
Step2: Burn a password reset disk with a blank CD/DVD or USB flash drive.
Step3: Boot the locked computer from the burned CD/DVD or USB.
Step4: Start to remove the forgotten or lost XP password. (Note: If your computer is a domain controller, you can also reset the forgotten Windows domain password in this step.)

One more tip: After you finish resetting Windows XP password lost, it is highly recommended to put up the burned CD/DVD or USB well in case you can use it in future.